ARGIA 287 
The gills are easily broken off the nymphs of this genus both in the 
laboratory and in life. If their loss occurs early in nymphal life, they 
are regenerated, and it is no uncommon thing to find a specimen with 
one, two or three of the gill plates of smaller size than normal. The 
loss of gills seems not to seriously affect the respiration of the nymphs. 
KEY TO THE SPECIES 
Adults 
1. Males 
1 The total area of dark color on abdominal segments 3-6, or the 
thoracic dorsum, or both, less than the pale area of the same 
Date ee rere eee Rt eee warts dean eet 2. 
The total area of dark color on the abdominal segments 3-6, and 
the thoracic dorsum, greater than the pale area of the same parts 
2 Black middorsal thoracic stripe a mere hair line. Antehumeral 
pale stripe very broad, 4-6 times as wide as the middorsal 
Ghee E NIG Me 38 recht as, i Aya ER RE GS A ee Meee 3. 
Black middorsal thoracic stripe wide. Antehumeral pale stripe 
narrow, one-half to one and one-half times as wide as the mid- 
CLOW SUTUDG se leet a itn acta HLM iho clr beni a see 6. 
3 Humeral black stripe reduced to a hair line and of uniform thick- 
ness throughout. its;entire length... 0/0022 >. cote sos cae. os 4, 
Humeral black stripe not of uniform thickness throughout, the 
ends being greatly thickened, while the median third or more 
is reduced. to a hair line or is absent... ....... 95... ua. 5. 
4 Head with some black markings around the vertex and bases of 
tie.antennage at least... ... 5s: . Ame ae biel! 2 4 «aloe tonto, p. 299 
Head with no black markings at all, pale colors being cream and 
ETC ®, SOON FL ROO: eat a I 1! Fe RnR ine Ca solita, p. 299 
5 Abdominal terga 3-5 with less than the basal half black. Posterior 
lobe of the prothorax pale. No black spot on abdominal segment 
CTE RD oypAgiM: 2k. ee OPH Ee ee emma, p. 294 
Abdominal terga 3-5 almost entirely black. Posterior lobe of the 
prothroax black. A black spot on the dorsum of abdominal 
RE RMEN TG OIE 28 is copes ecwrah gra cio tgs vacates apicalis, p. 292 
G mcbameral stripe forked aa) -witictAs st 5ee-tne egal eee ae os he 
EHamerali stripe not: forkeds.../. 0.1.5... i. ace eee ee ee 10. 
